In the Third Age, the Orcs of Angmar claimed it as their capital, which was one of the reasons for the Dwarves' special hatred of this people. After the fall of Angmar Gundabad remained an Orc stronghold, until it was cleaned of Orcs during the War of the Dwarves and Orcs. But the Orcs repopulated it over the next two hundred years, although after the Battle of Five Armies, there probably weren't as many.

Mount Gundabad was the rally point of the armies of Bolg the Goblin chieftain, who would later go on to fight the Battle of Five Armies.[1]

Etymology

Gundabad is a Khuzdul word of unknown meaning. The first element is probably Gund, meaning "excavated tunnel".